The C3b-dependent C3 convertase (C3bBb) of the alternative pathway is a key enzyme in the activation of complement and plays a fundamental role in acute and chronic inflammation. The research objective outlined in this proposal will attempt to assess functional properties of the active subunit of the C3 convertase (Bb) in terms of its biochemical structure. Specifically a major portion of the amino acid sequence of factor B and its activation peptides, Ba and Bb, will be determined. A variety of chemical and enzymatic cleavage techniques will be examined in order to optimize the generation of peptides. High-pressure liquid chromatography and microsequence technology will facilitate and expedite the isolation, sequencing, and alignment of individual peptide fragments. These investigations should help to reveal the chemical basis for factor B genetic polymorphism and will undoublty lead to a better understanding of the mechanism of action of factor B in complement activation.